<!DOCTYPE html>
<style>
.outer {
  width: 40px;
  height: 40px;
  display: flex;
  box-sizing: border-box;
}
.outer div {
  flex: 1;
}
.shadow {
  box-shadow: inset 0 0 0 5px blue;
}
.border {
  border: 10px solid transparent;
}
.radius {
  border-radius: 20px;
}
</style>
<div class="outer shadow"></div>
<div class="outer shadow"></div>
<div class="outer shadow"></div>
<div class="outer" style="padding: 10px"><div class="shadow"></div></div>
<div class="outer" style="padding: 10px"><div class="shadow radius"></div></div>
<div class="shadow radius" style="width: 20px; height: 20px"></div>
<div class="shadow radius" style="width: 20px; height: 20px"></div>
<div class="outer" style="padding: 10px"><div class="shadow radius"></div></div>
